Current ADSL modem system designs do not incorporate a low power transmission mode. Such systems require high power dissipation in the modem line driver, even when no data is being transmitted.
Accordingly, ITU contributions have proposed a low power mode (i.e., “Q-mode,”) in the transmitter. During the proposed Q-mode, the modem is still in the ready state, but enters a low power mode during periods of no data transmission.
ITU contributions, HC-029R1 and AB-045, formally define a semi-stationary Q-mode signal, that employs a pair of pseudo-random bit sequence (“PRBS”) generators, each with a period of greater than 4000. These proposals require two separate signals, namely, a stationary signal and a non-stationary signal. One problem with the resulting Q-mode signal is that it does not have a sufficiently low Peak-to-Average Ratio (“PAR”). The “Average” used may be, for example, the root-mean-square. A signal having a low PAR would enable the analog front end of the modem to reduce the amount of power dissipated in the line driver even further during Q-mode. By reducing power dissipation, a Q-mode signal having a low PAR would correspondingly reduce the amount of heat generated in cabinets containing ADSL equipment. A reduction in heat would in turn make it possible for ADSL service providers to either reduce the size of cabinets for the same number of ADSL modems, or to deploy more ADSL modems per cabinet than is possible with current Q-mode proposals.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.